The physical store behind "state store" is change-log kafka topic. In Kafka stream, if something fails in the middle, the "state store" is restored back to the state before the event happens at the first step / beginning of the stream.
On 2020/12/31 08:48:16, Pushkar Deole <pdeole2...@gmail.com> wrote: > Hi All, > > We use Kafka streams and may need to use exactly-once configuration for > some of the use cases. Currently, the application uses either local or > global state store to store state. > So, the application will consume events from source kafka topic, process > the events, for state stores it will use either local or global state store > of kafka, then produce events onto the destination topic. > > Question i have is: in the case of exactly-once setting, kafka streams > guarantees that all actions happen or nothing happens. So, in this case, > any state stored on the local or global state store will also be counted > under 'all or nothing' guarantee e.g. if event is consumed and state store > is updated, however some issue occurs before event is produced on > destination topic then will state store be restored back to the state > before it was updated for this event? >
